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Two-way temperature-regulating valve
Equipment-flow regulator

Fire Controlman Volume 04-Fire Control Maintenance Concepts
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FLOW  REGULATORS Many  different  types  and  sizes  of  flow-regulating devices  are  used  in  both  the  primary  and  secondary cooling  systems  to  reduce  the  pressure  or  flow  of coolant  through  a  cooling  system.  Figure  2-12  shows a   constant-flow   regulator. Figure 2-12.—Constant-flow regulator. The  orifice  plate  is  found  primarily  in  the  seawater cooling  system.  It  is  the  simplest  design  of  a  flow- regulating  device  and  consists  of  a  steel  plate  with  a hole  in  it.  With  constant  known  seawater  pressure  and with  a  given  hole  size,  the  volume  of  water  through the  device  can  be  determined.  The  use  of  an  orifice plate  is  limited  to  where  the  input  water  pressure  is essentially  constant,  such  as  the  ship’s  fire  main. The  orifice  plate  is  normally  installed  between two  pieces  of  flanged  pipes  upstream  from  the  heat exchanger.  This  reduces  the  ship’s  fire-main  pressure below  the  pressure  in  the  secondary  cooling  system. If  one  of  the  heat  exchanger  tubes  fails,  the  seawater pressure   will   be   lower   than   the   distilled-water   pres- sure;  therefore,  it  will  not  contaminate  the  secondary cooling  system,  as  the  secondary  cooling  system  will force  distilled  water  into  the  primary  cooling  system. A  ruptured  heat  exchanger  tube  or  a  bad  single- tube sheet in a heat exchanger will give no visual indi- cation  of  water  loss  except  for  the  indication  on  the expansion  tank  sight  glass. To  stabilize  the  flow  of  seawater  and  to  prevent  jet erosion  of  the  heat  exchanger  and  associated  piping, the  orifice  plate  should  be  installed  with  at  least  15 pipe  diameters  of  straight  pipe  upstream  from  the  heat exchanger.  When  there  is  a  drop  in  the  heat  exchanger primary  input  pressure  and  the  seawater  supply  pres- sure  has  not  changed,  you  should  first  check  the  du- plex  strainer  differential  pressure  gage  to  ensure  that the  duplex  strainer  is  clean.  Then  you  should  inspect the   orifice   plate   for   deposits   or   particles   that   could restrict   the   seawater   flow.   Also,   you   should   inspect the  orifice  plate  for  erosion  damage  of  the  hole  diam- eter.  (Replace  the  orifice  plate  when  there  is  an  in- creased   flow   of   seawater   to   the   point   that   it   could damage   the   heat   exchanger.) Never  use  the  seawater  valves  to  throttle  (partially close)  the  flow  of  seawater  in  the  primary  cooling  sys- tem,  because  the  seawater  will  erode  the  internal  parts of  the  valve.  Such  misuse  would  damage  the  valve,  re- quiring   extensive   repair   or   replacement   because   it would  no  longer  close  properly. When   used   with   the   chilled-water   system,   the constant-flow   regulator   (variable   orifice)   is   installed downstream  from  the  heat  exchanger.  This  restricts the  flow  from  the  heat  exchanger  and  keeps  the  heat exchanger  fully  submerged  for  greater  efficiency  (heat transfer).  This  flow  regulator  is  not  used  in  the  sea- water  system  because  the  internal  parts  would  easily become  fouled  with  marine  growth  and  deposits.  The operation  is  dependent  on  the  movement  of  the  orifice plugs  (neoprene)  to  regulate  the  flow  of  water. The  equipment-flow  regulator  is  used  primarily with  electronic  equipment  to  regulate  the  flow  of  dis- tilled   water   through   the   individual   cabinets   and components.  It  maintains  a  constant  flow  of  distilled water  with  limited  changes  in  the  input  pressure.  At the  minimum  water  flow,  the  total  amount  of  water  is passed  through  the  device.  As  the  flow  of  water  in- creases  to  the  flow  regulator’s  maximum  limit,  the water  flow  is  restricted  by  the  movement  of  the  insert, which  causes  the  hole  size  to  decrease,  thereby  regu- lating  the  flow  of  water.  The  amount  of  water  that  the flow  regulator  will  pass  is  usually  stamped  on  the  side of  the  regulator.  This  is  because  the  external  dimen- 2-15






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